A comparison of selected heavy metals in soils mixed with domestic and industrial sludges and assessment of effects of the sludge pollutants on oxidative stress markers of the African kale (Brassica oleracea var acephala) grown using sewage sludge manure

Sewage sludge is used as fertiliser and contains nutrients required for plant growth. It also contaminants that can leach into crops. The effects of sewage on kale plants were investigated. Mixture ratios 50:50 20:80 soil prepared. soil-sludge blends analysed selected metal residues. Kale seedlings 10-13 cm planted the different combinations. Leaf lengths measured 21 days post transplanting four weeks. After sixty days, leaves residue levels antioxidant enzyme activities. results showed higher concentrations in blended with industrial than mixed domestic sludge. highest growth was observed after 28 grown 50% soil-industrial mixtures. Superoxide dismutase glutathione peroxidase activities applied when compared to sludge-free soil. high metals enhanced activity attributed Preassessment be manure recommended safeguard health and, indirectly, humans who consume crops.    Key words: sludge, metals, pollutants, plants.